The focus of this project is to gain new knowledge regarding the very early events following mucosal transmission of HIV. We are particularly focused on molecular interactions between the viral envelope and cell surface receptors that are expressed on CD4 + T cells. This information is fundamental to the development of an effective HIV vaccine. We have shown previously that the infection of a4b7-expressing CD4+ T cells is one of these early events. In addition, we showed that the HIV envelope protein gp120 binds directly to integrin a4b7 and that this interaction is mediated by the V2 domain of gp120. Our approach in 2019 was to define the types of monoclonal antibodies that interfere with this interaction. Such information will hopefully aid in the design and development of an effective HIV vaccine.